Interspecific Hybridization in Haplopappus and Its Bearing on Chromosome Evolution in the Blepharodon Section

Jackson, R. C.

doi:10.2307/2439027

Cited by 45 publications

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“…T h e position of this weak point in chromosome 2 corresponds wit11 that of the only region \vhich displayed negative heteropycnosis in prophase and metaphase during the current investigation. Jackson (1962) suggested that H. gracilis (72 = 2 ) evolved from H. r~velzii ( n = 4 ) b y a process of unequal reciprocal translocations, .ivhich resulted in the loss of centromeres. Such a inechanisn~ for reduction in chromoson~e number was proposed by Robertson (1916), and was further developed by Navashin (1932).…”

Section: Resultsmentioning

confidence: 99%

DISTRIBUTION OF HETEROCHROMATIN IN THE CHROMOSOMES OFHAPLOPAPPUS GRACILIS

Ames¹,

Mitra²

1968

Can. J. Genet. Cytol.

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Several approaohes wcre employed to study the distribution of hetcrochromatin in root tip chromoson~es of Hnplopnppzu gmczlis. Cold treatment and prerrcahncnt in an aqucous solution of 8-liydrosyquinolinc revealed achromatic paps in metaphase chromosomes. Cold treatment also permitted thc demonstra- 3.tlon of positive heteropycnosis in prophase chrolnosonies. Further support for the identification of hetcrochromatic sxgnents was probided by a study of the localization of chromosome aberrations induced by malelc hydrazide and an analysis of the pattern of D N A synthesis in chromosomes of root tip cells. Seven of the tell regions that were preferentially broltcn by ~naleic hydrazide also reacted differentially to cold treatment or to pretreatment with 8-hydroryquinoline. A good corrclntion was found betwccn regions that completed D N A replication late in the DNA-synahetic pcriod and segments that werc slio\vn t o be hetcrochromatic by the other techniques.

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Section: Resultsmentioning

confidence: 99%

DISTRIBUTION OF HETEROCHROMATIN IN THE CHROMOSOMES OFHAPLOPAPPUS GRACILIS

Ames¹,

Mitra²

1968

Can. J. Genet. Cytol.

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“…Pollen grains with the cytoplasm stained a uniform dark blue were considered viable; those stained only in spots or not at all were counted as non-viable. The 2 longest chromosomes with a submedian centromere is the Ag pair, and the 2 shorter ones with subterminal centromeres and secondary constrictions in their short arms is the Bg pair (Jackson, 1959(Jackson, , 1962. 1).…”

Section: Ma/terials and Methodsmentioning

confidence: 99%

“…CYTOLOGY OF THE DIFFERENT CHROMOSOME TYPES The diploid karyotype of typical H. gracilis is composed of 4 chromosomes (Fig. Meiosis in H. gracilis has been described in detail elsewhere (Jackson, 1959), but a metaphase I stage is shown (Fig. The 2 longest chromosomes with a submedian centromere is the Ag pair, and the 2 shorter ones with subterminal centromeres and secondary constrictions in their short arms is the Bg pair (Jackson, 1959(Jackson, , 1962.…”

Section: Ma/terials and Methodsmentioning

confidence: 99%

“…JACKSON CYTOGENETIC STUDY OF HAPLOPAPPUS 947 of centromneres. Except for 2 easily recognized types of supernumerary chromosomes (Jackson, 1960), chromosome counts from throughout the range of H. gracilis have shown the species to be uniformly n = 2. Similar aneuploid changes have been suggested for a number of animal species (White, 1954) and have been well documented in Diptera, particularly in Drosophila for which Dubinin (1934Dubinin ( , 1935 provided experimental proof of the process.…”

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A Cytogenetic Study of a Three-Paired Race of Haplopappus gracilis

Jackson

1965

American Journal of Botany

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“…Series of conspicuous reductions in chromosome number have been reported in Mediterranean Crepis (Babcock 1947), Australian Calotis (Stace 1978(Stace ,1982, and North American Haplopappus (Jackson 1962, Smith 1966. All of these reductions in chromosome number have been observed in plant groups growing in unstable habitats comprising semidesert regions or seasonally xeric areas, and these reductions have been associated with the evolution of annual habit.…”

Section: Changes In Karyotype and Chromosome Numbermentioning

confidence: 98%

Chromosomal Evolution in the Genus Brachyscome (Asteraceae, Astereae): Statistical Tests Regarding Correlation Between Changes in Karyotype and Habit Using Phylogenetic Information

et al. 1999

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Karyotype analyses were carried out on 73taxa of Brachyscm and Btaxa of its allied genera, Australian Astereae. Statistical tests regarding correlations between changes in chromosome number, total chromosome length, mean chromosome length, karyotypic asymmetry and chromosome length heterogeneity and changes in habd were performed based on the matK molecular phylogenetic tree. The reductions in chromosome number and total chromosome length, and the increases in mean chromosome length, chromosome length heterogeneity and karyotypic asymmetry were found to be correlated with the change in habit from perennial to annual. A reduction in total chromosome length is favored to shorten the mitotic cell cycle and to produce smaller cells conducive to more rapid development of smaller annuals under the time-limited environment. Stepwise dysploidal reductions in chromosome number were achieved through the translocation of large chromosome segments onto other chromosomes, followed by the loss of a centromere, resulting in one fewer linkage group and one fewer haploid chromosome. The correlations between the dysploidal reduction in chromosome number and the increases in mean chromosome length, length heterogeneity and asymmetry in karyotype can be attributed to this mode of chromosomal change. These changes occurred independently in several different lineages in Brachyscom.

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Interspecific Hybridization in Haplopappus and Its Bearing on Chromosome Evolution in the Blepharodon Section

Cited by 45 publications

References 0 publications

DISTRIBUTION OF HETEROCHROMATIN IN THE CHROMOSOMES OFHAPLOPAPPUS GRACILIS

DISTRIBUTION OF HETEROCHROMATIN IN THE CHROMOSOMES OFHAPLOPAPPUS GRACILIS

A Cytogenetic Study of a Three-Paired Race of Haplopappus gracilis

Chromosomal Evolution in the Genus Brachyscome (Asteraceae, Astereae): Statistical Tests Regarding Correlation Between Changes in Karyotype and Habit Using Phylogenetic Information

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